1. Field of the Invention
The present invention relates generally to a communication network, a path setting method, a network management system and a node. More particularly, the invention relates to a hierarchical path setting system in a communication network, in which paths having mutually different granularities are present in admixing manner.
2. Description of the Related Art
Currently, in communication network, attempt is made for establishing paths having variety of granularities. For example, in an internet draft “draft-ietf-mpls-generalized-signaling-04.txt” (reference 1) of IETF (Internet Engineering Task Force), there has been proposed to establish ATM (asynchronous Transfer Mode) path, VP/VC (Virtual Pass/Virtual Channel) path, SONET (Synchronous Optical Network)/SDH (Synchronous Digital Hierarchy) path, wavelength/waveband path, fiber path and so forth.
In the network containing a plurality of paths having mutually different granularities, the paths have conventionally been hierarchized per granularities, lower order paths aggregated per sub-networks are set via higher order paths. Here, the lower order path represents a path having smaller granularity, and the higher order path represents a path having greater granularity.
It becomes possible to switch, the paths having smaller granularity set in the same route with the paths of greater granularity in multiplexing manner by hierarchizing the paths to permit advantageously reduce a size of cross connect. On the other hand, the user may demand setting of paths of variety of granularities, such as 155 Mbit/s, . . . 2. g Gbit/s, 10 Gbit/s and so forth, adapting to application.
The network having hierarchical has been disclosed in Suemura et al., “Control of Hierarchical Paths in Optical Network”, PNI2000-37, the Institute of Electronics Information and Communication Engineers, Japan, (reference 2), for example.
As one prior art, general network construction shown in the reference 1 is illustrated in FIG. 12. The network consisted of optical network devices 102-1 to 102-16 having wavelength path is divided into a plurality of sub-networks 100-1 to 100-4 depending upon geographical information, convenience in management or the like. These plurality of sub-networks are connected to by optical network devices 101-1 to 101-6 handling waveband path, one or more of which is provided in each sub-network. As set forth above, the network handling the wavelength paths and the network handling the waveband path are hierarchized.
In such network, the optical paths are classified to paths set in the sub-network and paths set bridging sub-net works. Paths set from the optical network devices 102-9 to 102-12 are established only by wavelength paths in the sub-network via the optical network device 102-11. On the other hand, the path set from the optical network device 102-1 to 102-16 is established by the wavelength paths in the sub-network and the waveband paths between the sub-networks via the optical network devices 102-2, 101-1, 101-5, 101-3 and 102-14.
The reference 2 as the second prior art also discloses setting of hierarchized path without dividing the network into sub-networks. Amongst, all nodes forming the network have construction for switching the wavelength paths and the waveband paths. In such network, when a setting demand of the wavelength path is given, a method deriving the shortest route to a receiver node by using CSPF (Constraint Shortest Path Fast) algorithm which calculates a routing path in consideration of only links having vacant wavelength and setting the wavelength paths along the calculated path, is repeated. When a number of the wavelength paths along certain route reaches a number to form the waveband path, aggregate of the wavelength paths is switched into the waveband path. In the foregoing procedure, hierarchized path is established by the wavelength paths and the waveband paths.
A first problem encountered in the first prior art is to waste network resource upon occurrence of demand not matching with traffic patterns used in designing since the sub-networks are preliminarily designed in fixed manner. For example, when one demand for lower order path between the sub-networks is present, remaining bands are wasted within the higher order path connecting between the sub-networks.
A second problem encountered in the first prior art is that failure of the node handling the higher order paths influences for all of the networks. Since the sub-networks are preliminarily designed in fixed manner, the nodes handling the higher order paths are determined in similar manner. Therefore, when failure is caused in the node handling the higher order paths, the path bridging between the sub-networks cannot be set since the higher order path cannot be set.
A problem in the second prior art is incapability of efficiently multiplexing the lower order paths into the higher order path. While the second prior art can solve the second problem in the first prior art, it is not possible to intentionally aggregate lower order paths in the same route to switch into the higher order path. As a result, since the higher order path cannot be established efficiently, advantage of hierarchizing of the path can be degraded.